The present invention relates to a novel process for preparing 1,3,5,7-tetraacetamidoadamantane, which provides an improved route to 1,3,5,7-tetraaminoadamantane. The latter compound is an intermediate useful for preparing the novel explosive 1,3,5,7 tetranitroadamantane, which is the subject of a copending U.S. patent application of Everett E. Gilbert and Gilbert P. Sollott entitled "1,3,5,7 Tetranitroadamantane and Process for Prepariang Same", Ser. No. 196,956, filed Oct. 14, 1980.
Adamantane is also known by the scientific name of tricyclo [3.3.1.1.sup.3,7 ] decane. Adamantanes containing substitutents in the 1,3,5 and 7 positions, as discussed hereinafter, are represented by the following general formula:
______________________________________ Compound R ______________________________________ ##STR1## I II III IV V VI H Br I NHCOCH.sub.3 NH.sub.2 NO.sub.2 ______________________________________
1,3,5,7-Tetraminoadamantane (V) is a known compound, which in the past has been prepared by Hoffmann degradation of 1,3,5,7-adamantanetetracarboxamide produced from 1,3,5,7-adamantanetetracarboxylic acid. However, the tetracarboxylic acid was prepared in very low overall yield by a laborious, multistep procedure involving the Meerwein ester synthesis (H. Stetter and M. Krause, Liebigs Ann. Chem., 717,60 (1968); Tetrahedron Letters, 19,1841 (1967)).
The present invention is directed to a new route for preparing 1,3,5,7-tetraaminoadamantane from 1,3,5,7-tetraiodoadamantane, which makes the compound more readily accessible.
It is known that 1-amino-, 1-acetamido-, 1-toluenesulfamido-, 1-cyano-, and 1-carboxy-adamantanes can be easily prepared by reacting the readily accessible 1-bromoadamantane with ammonia, acetamide, or acetonitrile and sulfuric acid (the latter known as the Ritter reaction), sodium toluenesulfonamide, cuprous cyanide and pyridine, and formic acid in fuming sulfuric acid. resp. These reactions in most cases can be extended to the preparation of the analogous 1,3-disubstituted compounds. However, attempts to prepare the analogous 1,3,5,7-tetrasubstituted adamantanes by the same types of reactions from the readily accessible 1,3,5,7-tetrabromoadamantane (II) have not been successful. Thus, Stetter and Krause (ibid) reported that they were unable to prepare 1,3,5,7-tetracarboxy--and 1,3,5,7-tetraacetamidoadamantanes (IV) in this manner. Similarly, E.E. Gilbert (U.S. Army Armament Research and Development Command, Large Caliber Weapons Systems Laboratory, Dover, N.J.) has been unable to prepare 1,3,5,7-tetraaminoadamantane and the corresponding tetracyano--and tetrakis (toluenesulfonamido) compounds from the tetrabromo compound.
E.E. Gilbert, like Stetter and Krause, has found that 1,3,5,7-tetrabromoadamantane does not undergo the Ritter reaction. In the Ritter reaction, a carbonium ion, generated, for example, from mono- or dibromoadamantane with concentrated sulfuric acid with or without silver sulfate present, interacts with a nitrile, and the nitrilium ion thus formed is converted by water to the amide. (Stetter and Krause, loc. cit. T. Sasaki, S. Eguchi, and T. Toru, Bull. Chem. Soc. Japan, 41,236 (1968), and refs. cited therein.) ##STR2## An attempted reaction of 1,3,5,7-tetraiodoadamantane (II) under similar conditions was also unsuccessful.